Currently, local telephone service is provided by a single company, such as a Regional Bell Operating Company (RBOC). These companies basically enjoy a monopoly over local telephone service within their regions. Thus, efforts are being made to introduce competition into the local telephone market to eliminate the monopolies. Under the current system, however, if customers want to change from one service provider to another, they must also change their telephone numbers. This inhibits telephone customers' willingness to switch to an alternate service provider.
To allevoate the problem, the Federal Communications Commission (FCC) has issued an order for Number Portability (NP) which, in addition to providing other features, will allow a customer to switch between local service providers while keeping the same telephone number. In the first phase of NP, known as Local Service Provider Portability, the customer's geographic location does not change. In the second phase of NP, known as Portability Outside the Rate Center, the customer will have the option to change geographic locations and retain their telephone number.
The public telephone network consists of a large number of switches, such as Lucent Technologies' No. 5ESS, each serving about 10 k to 100 k customers. When a customer dials a number, the customer's serving switch (the originating switch) must allocate a route to the switch serving the dialed number (the destination/provider switch). In the existing telephone network, the first six digits (NPA-NXX) of a 10 digit telephone number identify a particular switch in a particular geographic region. Switches can route calls between switches based on the NPA-NXX of the dialed number. With Local Service Provider Number Portability, the NPA-NXX of the dialed number unambiguously identifies the geographic location of the customer.
Current proposals for the first phase of NP involve storing an identifier corresponding to the switch (the Location Routing Number or LRN) to which a subscriber's service has been ported in a large, special purpose computers, known as service control points (SCP). The chosen implementation for NP in most jurisdictions is for the switch originating a call to query the SCP for an LRN. routing address on every in switch call to a portable NPA-NXX. (A portable NPA-NXX is one in which at least one number has ported from one service provider to another.) The LRN is used to address the switch (the Recipient Switch) to which the call should terminate. Although the LRN is a 10-digit number, the switch uses only the first 6-digits, i.e., NPA-NXX of the LRN, to route the call. The call is routed on these 6-digits of the LRN as though the switch were acting on the NPA-NXX of dialed telephone number. The same routing tables are used because the portability of the customer is restricted to the boundaries of the established rate centers, i.e., there is no location portability outside these rate centers. As a result of this restriction to portability within the rate centers, call typing, carrier selection, distance rating, and generation of billing information can be determined accurately by using the dialed telephone number without any additional information. Although the customer has been ported from one service provider to another, the geographic relationship between the dialed NPA-NXX and the defined geographic location of the called customer is unbroken.
With Portability Outside the Rate Center, however, this relationship between the NPA-NXX and the geographic location of a customer is broken, such that there is no fixed relationship between the dialed telephone number and its geographic location.
Separating the relationship between a telephone number and its geographic location has an impact on other aspects of the telephone network which are necessary for providing telephone service. As an example telephone service pricing and billing are dependant on the relationship between the telephone number and the geographic location of the subscriber. Carrier selection during call processing is also dependent on this relationship.
The impact on telephone service pricing is as follows. If it is assumed that distance sensitivity will remain as one of the two major factors (along with call duration) in the pricing of a telephone call, then it follows that a geographic location must continue to be associated with both the Calling Number and Called Number for telephony services. As generally defined by the FCC and other regulatory bodies, the distance of a telephone call is the airline mileage between the calling party and the called party as measured using geographic coordinates assigned to the "Rate Centers" in which the Calling Party and Called Party are located. Today, with limited exceptions, the same Rate Center is used for every line number of an NPA-NXX. If a telephone number is ported outside its geographic area in which its NPA-NXX is defined, then some designation for the geographic location must be found.
The NPA-NXX today is not only used for "toll" rating between rate centers, but also to define boundaries for various types of Local Service, such as Local Measured Service, Message Unit Service and other variations on the theme of usage sensitive measurements for local service. Switching systems are programmed via translations to route and rate telephone calls based on table relationships between the Calling Party Number and Called Party Number and other factors such as the Calling Party Class of Service. Removing the geographic significance of the NPA-NXX putt the on-going viability of these translation tables, and thus the services that they define and enable, in jeopardy of no longer being able to work at all.
It is also critical to note that geographic boundaries implied by the NPA-NXX play a central role in carrier selection, in that the rules used today to separate the realms of competition (i.e. Local Exchange Service, Intrastate Toll, Interstate Toll) are based on the relationship of the Calling Party NPA-NXX to the Called Party NPA-NXX. The NPA-NXX relationship between the Calling and Called Parties is the key component in the logic of the switching system used to determine to which transport carrier the call must be handed off for delivery to the Called Party.
Accordingly, it is an object of our invention to provide a method and system for providing local number portability that overcome the restrictions of the prior art and enables continued use of existing systems and structures which are based on the relationship of the telephone number to the rated center from which the users service is provided.